Guards for cutting instruments

Abstract

A guard for moving-blade cutting instruments, for instance band-saws and band-knives. The guard is in the form of a comb or other toothed member, mounted alongside the blade and vibrated cyclically so that the tips of the teeth lie proud of the cutting edge at least once per cycle. The clearances between the teeth are aligned so as to facilitate access of piles of cloth or the like to the blade, but the bulkier fingers of the operator should be struck by the tips of the vibrating comb and repelled before being seriously cut, or cut at all, by the blade. The guard may be mounted to yield within limits, so as to increase the exposure of the blade, when subjected to sustained pressure from approaching work.

I claim: 
     
       1. For use with a moving-blade cutting instrument, a guard comprising: a toothed member for mounting alongside said moving blade;   motor means to vibrate said toothed member cyclically;   points presented by the teeth of said toothed member;   said points lying slightly proud relative to said moving blade at at least one moment in the cycle of said cyclical vibration.   
     
     
       2. A guard according to claim 1, in which said toothed member is of comb-like form, in which clearances separate said teeth of said comb-like toothed member, and in which said teeth and said clearances are aligned with the direction in which work to be cut moves past said moving blade during use. 
     
     
       3. A guard according to claim 2, in which said toothed member is mounted to vibrate in a plane substantially parallel both to said moving blade and to said direction in which work moves past said moving blade during use. 
     
     
       4. A guard according to claim 1 having two of said toothed members, one located to each side of said moving blade. 
     
     
       5. A guard according to claim 4 including a unitary structure of "U"-section, in which said moving blade lies within said "U" and in which said two toothed members constitute the two legs of said "U". 
     
     
       6. A guard according to claim 1 including a pivotal mounting which enables said guard to deflect, within a limited distance, when work is advanced towards said moving blade and makes contact with said guard. 
     
     
       7. A guard according to claim 6 in which said pivotal mounting includes biassing means to bias said guard to its normal, undeflected position. 
     
     
       8. A guard according to claim 7 in which said motor means constitutes said biassing means. 
     
     
       9. A cutting instrument comprising: a moving cutting blade;   a toothed comb-like member mounted alongside said blade;   means to vibrate said toothed member cyclically;   points presented by the teeth of said comb-like toothed member, the mode of said cyclical vibration being such that said points lie slightly proud of said moving blade at at least one moment in said cycle of vibration;   a working surface over which work may be caused to slide to approach said blade and said toothed member, and a hole formed in said working surface, said moving blade and said toothed member extending on both sides of said working surface and passing through said hole.